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K100-forum.com » Technical, repair and troubleshooting » Engine and transmission » K100RT issues with fuel pump

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1Back to top Go down   K100RT issues with fuel pump Empty K100RT issues with fuel pump Sun Sep 15, 2024 10:09 pm

agbikeadv

agbikeadv
New member
New member
Hi,

Purchased an 87 K100RT a few months back which had sat idle for unknown years and I am finally getting around to getting it back on the road. Have replaced the fuel pump, filter, hoses, fuel sender unit, relay and battery. I haven't taken the injectors out nor replaced air filter as yet but that's on the cards in coming week or so.

My initial query relates to the fuel pump etc. When I turn power/ignition key on there is no 'prime up' sound coming from the fuel pump. When I press the start button the bike turns over but doesn't start and when I let go of the start button the fuel pump can then be heard for a second or two. Have seen numerous 'how to' videos where you can hear the fuel pump engaging when first turning key but mine not doing so. Thoughts?

Thankyou

Tony

    

2Back to top Go down   K100RT issues with fuel pump Empty Re: K100RT issues with fuel pump Sun Sep 15, 2024 11:01 pm

Point-Seven-five

Point-Seven-five
Life time member
Life time member
The four valve engines with the Motronic prime the pump when the key is turned on before cranking the engine.  Those are the K100RS from the 90's and the K1100 models.

Two valve engines with the Jetronic don't energize the fuel pump until the engine is cranking and then continues to run the pump for an additional second or so after cranking stops if the engine doesn't start.

So on your bike you will not hear the fuel pump before cranking.  Then you should hear it briefly when the cranking stops.  If the engine starts, the pump will continue to run as long as the rpm are above 700.


__________________________________________________
Present: 1991 K100RS "Moby Brick Too"
 
Past:
1994 K75RT "Ilsa, She Wolf of the SS"
1988 K100RS SE "Special Ed"
1994 K75S "Cheetos"
1992 K100RS "Moby Brick" R.I.P.
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

3Back to top Go down   K100RT issues with fuel pump Empty Re: K100RT issues with fuel pump Mon Sep 16, 2024 8:34 am

agbikeadv

agbikeadv
New member
New member
Point-Seven-five wrote:The four valve engines with the Motronic prime the pump when the key is turned on before cranking the engine.  Those are the K100RS from the 90's and the K1100 models.

Two valve engines with the Jetronic don't energize the fuel pump until the engine is cranking and then continues to run the pump for an additional second or so after cranking stops if the engine doesn't start.

So on your bike you will not hear the fuel pump before cranking.  Then you should hear it briefly when the cranking stops.  If the engine starts, the pump will continue to run as long as the rpm are above 700.
Thankyou so much. A great explanation.

    

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